High Harmonic Generation by Guided Surface Plasmon Polaritons

摘要

We discuss how the intriguing phenomenon of surface plasmon resonance (SPR) can be exploited in enhancing the intensity field of the incident femtosecond laser for the purpose of high harmonic generation (HHG). We first summarize our previous attempt made with a 2-D planar nanostructure comprised of metallic bow-tie nano-antennas, which enabled us to generate up to 21st harmonics from Xenon gas using 1-nJ pulse energy with an intensity enhancement factor of ~20 dB. Then we describe another attempt currently being made by devising a 3-D nano-waveguide with the aim of improving the HHG conversion efficiency by expanding the localized volume of field enhancement by means of propagating surface plasmon polaritons (SPPs). Our finite-difference time-domain (FDTD) calculation shows that the enhanced volume can be increased significantly by optimal selection of the waveguide's geometrical parameters as verified in our preliminary experimental results.